Device and method of handling narrowband internet of things communication

ABSTRACT

A communication device for handling a narrowband internet of things (NB-IoT) communication comprises a storage device for storing instructions and a processing circuit coupled to the storage device. The processing circuit is configured to execute the instructions stored in the storage device. The instructions comprise receiving a SystemInformationBlockType2-NB message broadcasted by a base station (BS) on an NB-IoT cell; receiving an RRCConnectionReconfiguration-NB message indicating a full configuration, from the BS on the NB-IoT cell; and using a plurality of values for timers T301, T310, T311 and constants N310, N311 in response to the RRCConnectionReconfiguration-NB message, wherein the values are comprised in the SystemInformationBlockType2-NB.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/372,766 filed on Aug. 9, 2016, which is incorporated herein byreference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a device and a method used in awireless communication system, and more particularly, to a device and amethod of handling a narrowband internet of things (NB-IoT)communication.

2. Description of the Prior Art

In a long-term evolution (LTE) system, a radio access network known asan evolved universal terrestrial radio access network (E-UTRAN) includesat least one evolved Node-B (eNB) for communicating with a userequipment (UE), and for communicating with a core network. The corenetwork may include mobility management and Quality of Service (QoS)control for the UE.

SUMMARY OF THE INVENTION

The present invention therefore provides a communication device andmethod for handling a narrowband Internet of Things (NB-IoT)communication to solve the abovementioned problem.

A communication device for handling a narrowband internet of things(NB-IoT) communication comprises a storage device for storinginstructions and a processing circuit coupled to the storage device. Theprocessing circuit is configured to execute the instructions stored inthe storage device. The instructions comprise receiving aSystemInformationBlockType2-NB message broadcasted by a base station(BS) on an NB-IoT cell; receiving an RRCConnectionReconfiguration-NBmessage indicating a full configuration, from the BS on the NB-IoT cell;and using a plurality of values for timers T301, T310, T311 andconstants N310, N311 in response to the RRCConnectionReconfiguration-NBmessage, wherein the values are comprised in theSystemInformationBlockType2-NB.

A communication device for handling a narrowband internet of things(NB-IoT) communication comprises a storage device for storinginstructions and a processing circuit coupled to the storage device. Theprocessing circuit is configured to execute the instructions stored inthe storage device. The instructions comprise initiating a RRCconnection reestablishment procedure for a NB-IoT communication;selecting a NB-IoT cell, when initiating the RRC connectionreestablishment procedure; receiving a SystemInformationBlockType2-NBmessage broadcasted by the NB-IoT cell; and using atimeAlignmentTimerCommon comprised in the SystemInformationBlockType2-NBfor a UL transmission.

A communication device for handling a narrowband internet of things(NB-IoT) communication comprises a storage device for storinginstructions and a processing circuit coupled to the storage device. Theprocessing circuit is configured to execute the instructions stored inthe storage device. The instructions comprise initiating a RRCconnection reestablishment procedure for a NB-IoT communication;selecting a LTE cell, when initiating the RRC connection reestablishmentprocedure; and terminating the RRC connection reestablishment procedureand entering an idle mode, when selecting the LTE cell.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a wireless communication systemaccording to an example of the present invention.

FIG. 2 is a schematic diagram of a communication device according to anexample of the present invention.

FIG. 3 is a flowchart of a process according to an example of thepresent invention.

FIG. 4 is a flowchart of a process according to an example of thepresent invention.

FIG. 5 is a flowchart of a process according to an example of thepresent invention.

FIG. 6 is a flowchart of a process according to an example of thepresent invention.

FIG. 7 is a flowchart of a process according to an example of thepresent invention.

DETAILED DESCRIPTION

FIG. 1 is a schematic diagram of a wireless communication system 10according to an example of the present invention. The wirelesscommunication system 10 is briefly composed of a network and a pluralityof communication devices. The network and a communication devicecommunicate with each other via a cell on one or more carriers.

In FIG. 1, the network and the communication devices are simply utilizedfor illustrating the structure of the wireless communication system 10.The network may include a radio access network (RAN) including at leastone base station (BS). The RAN may be an evolved universal terrestrialradio access network (E-UTRAN) including at least one evolved Node-B(eNB). The RAN may be a fifth generation (5G) network including at leastone 5G BS (e.g., gNB) which employs orthogonal frequency-divisionmultiplexing (OFDM) and/or non-OFDM and a transmission time interval(TTI) shorter than 1 ms (e.g. 100 or 200 microseconds), to communicatewith the communication devices. In general, a BS may also be used torefer any of the eNB and the 5G BS. Furthermore, the network may alsoinclude a core network which includes network entities connecting to theRAN.

A communication device may be a user equipment (UE), a narrowbandInternet of Things (NB-IoT) UE, a machine type communication (MTC)device, a mobile phone, a laptop, a tablet computer, an electronic book,a portable computer system, a vehicle, or an aircraft. In addition, thenetwork and the communication device can be seen as a transmitter or areceiver according to direction (i.e., transmission direction), e.g.,for an uplink (UL), the communication device is the transmitter and thenetwork is the receiver, and for a downlink (DL), the network is thetransmitter and the communication device is the receiver.

FIG. 2 is a schematic diagram of a communication device 20 according toan example of the present invention. The communication device 20 may bea communication device or the network shown in FIG. 1, but is notlimited herein. The communication device 20 may include a processingcircuit 200 such as a microprocessor or Application Specific IntegratedCircuit (ASIC), a storage device 210 and a communication interfacingdevice 220. The storage device 210 may be any data storage device thatmay store a program code 214, accessed and executed by the processingcircuit 200. Examples of the storage device 210 include but are notlimited to a subscriber identity module (SIM), read-only memory (ROM),flash memory, random-access memory (RAM), hard disk, optical datastorage device, non-volatile storage device, non-transitorycomputer-readable medium (e.g., tangible media), etc. The communicationinterfacing device 220 includes a transceiver transmitting and receivingsignals (e.g., data, messages and/or packets) according to processingresults of the processing circuit 200.

In the following embodiments, a UE is used to represent a communicationdevice in FIG. 1, to simplify the illustration of the embodiments.

A scenario assumed according to an example of the present invention isstated as follows. A NB-IoT UE may be configured with a radio resourcecontrol (RRC) connection by a BS. When the NB-IoT UE receives anRRCConnectionReconfiguration-NB message which indicates a fullconfiguration but does not include a mobilityControlInfo, the UE usesvalues for timers T301, T310, T311 and constants N310, N311, as includedin ue-TimersAndConstants received in SystemInformationBlockType2.However, the NB-IoT UE may not be able to receive theSystemInformationBlockType2, since the NB-IoT UE may not be capable ofperforming a LTE communication. Thus, the UE does not have the valuesfor the timers T301, T310, T311 and the constants N310, N311.

FIG. 3 is a flowchart of a process 30 according to an example of thepresent invention. The process 30 may be utilized in a UE (e.g., NB-IoTUE) to communicate with a BS (e.g., in the network in FIG. 1), andincludes the following steps:

Step 300: Start.

Step 302: Receive a SystemInformationBlockType2-NB message broadcastedby a BS on an NB-IoT cell.

Step 304: Receive an RRCConnectionReconfiguration-NB message indicatinga full configuration, from the BS on the NB-IoT cell.

Step 306: Use a plurality of values for timers T301, T310, T311 andconstants N310, N311 in response to the RRCConnectionReconfiguration-NBmessage, wherein the plurality of values are comprised in theSystemInformationBlockType2-NB.

Step 308: End.

According to the process 30, the UE receives aSystemInformationBlockType2-NB message broadcasted by a BS on a NB-IoTcell. The UE receives an RRCConnectionReconfiguration-NB messageindicating a full configuration, from the BS on the NB-IoT cell. The UEuses (e.g., applies) a plurality of values for timers T301, T310, T311and constants (i.e., for counter) N310, N311 in response to theRRCConnectionReconfiguration-NB message, wherein the plurality of valuesare included in the SystemInformationBlockType2-NB. Thus, the problemoccurs in the above scenario is solved.

Realization of the process 30 is not limited to the above description.The following examples may be applied to the process 30.

When starting the timers, the UE uses the plurality of values includedin the SystemInformationBlockType2-NB. When counting the number ofconsecutive “out-of-sync” indications for the NB-IoT cell, the UE usesthe constant for N310 in the SystemInformationBlockType2-NB. Whencounting the number of consecutive “in-sync” indications for the NB-IoTcell, the UE uses the constant for N311 in theSystemInformationBlockType2-NB. In one example, the UE starts the timerT310 when detecting N310 consecutive “out-of-sync” indications for theNB-IoT cell. When the timer T310 expires, the UE starts the timer T311.The UE starts the timer T301, when the UE selects the NB-IoT cell whilethe timer T311 is running. The UE stops the timer T310, when detectingN311 consecutive “in-sync” indications for the NB-IoT cell.

A scenario assumed according to an example of the present invention isstated as follows. A NB-IoT UE may be configured with a RRC connectionand a data radio bearer (DRB) by a BS. The NB-IoT UE may detect afailure on a radio link (e.g. radio link failure (RLF)) with the BS, andmay initiate a RRC connection reestablishment procedure. When the NB-IoTUE selects an NB-IoT cell, the NB-IoT UE is not able to receive aSystemInformationBlockType2 which is only broadcasted in a LTE cell.Thus, the NB-IoT UE is not able to apply a timeAlignmentTimerCommonincluded in the SystemInformationBlockType2.

FIG. 4 is a flowchart of a process 40 according to an example of thepresent invention. The process 40 may be utilized in a UE (e.g., NB-IoTUE) to communicate with a BS (e.g., in the network in FIG. 1), andincludes the following steps:

Step 400: Start.

Step 402: Initiate a RRC connection reestablishment procedure for aNB-IoT communication.

Step 404: Select a NB-IoT cell, when initiating the RRC connectionreestablishment procedure.

Step 406: Receive a SystemInformationBlockType2-NB message broadcastedby the NB-IoT cell.

Step 408: Use a timeAlignmentTimerCommon comprised in theSystemInformationBlockType2-NB for a UL transmission.

Step 410: End.

According to the process 40, the UE initiates a RRC connectionreestablishment procedure for a NB-IoT communication. The UE selects aNB-IoT cell, when initiating the RRC connection reestablishmentprocedure. The UE receives a SystemInformationBlockType2-NB messagebroadcasted by the NB-IoT cell. The UE uses (e.g., applies) atimeAlignmentTimerCommon comprised in theSystemInformationBlockType2-NB. Then, the UE transmits anRRCConnectionReestablishmentRequest-NB to the NB-IoT cell, receives aRRCConnectionReestablishment-NB from the NB-IoT cell, and transmits aRRCConnectionReestablishmentRequest-NB to the NB-IoT cell. Thus, theproblem occurs in the above scenario is solved.

Realization of the process 40 is not limited to the above description.The following examples may be applied to the process 40.

In one example, the step of using the timeAlignmentTimerCommon comprisesthat the UE starts a time alignment timer according to (e.g., by using)a value in the timeAlignmentTimerCommon when applying a timing advancecommand received from the NB-IoT cell. Further, the NB-IoT celltransmits a random access response comprising the timing advance commandto the UE, in response to a random access preamble received from the UE.The UE may transmit a RRCConnectionReestablishmentRequest-NB, afterreceiving the random access response. In one example, the NB-IoT celltransmits a Medium Access Control (MAC) Protocol Data Unit (PDU)comprising the timing advance command to the UE, after performing theRRC connection reestablishment procedure with the UE. In the aboveexamples, the operations of the NB-IoT cell may imply correspondingoperations of the UE, which are not narrated herein.

In one example, the process 30 may be combined with the process 40. TheUE receives a RRCConnectionReconfiguration-NB message indicating a fullconfiguration, from the NB-IoT cell, after completing the RRC connectionreestablishment procedure with the NB-IoT cell. The UE uses values fortimers T301, T310, T311 and constants N310, N311 in response to theRRCConnectionReconfiguration-NB message, wherein the values are includedin the SystemInformationBlockType2-NB.

A scenario assumed according to an example of the present invention isstated as follows. A NB-IoT UE is configured with a RRC connection and aDRB by a first BS. The NB-IoT UE may detect a failure on a radio link(e.g., RLF) with the first BS, and may initiate a RRC connectionreestablishment procedure in response to the RLF. The NB-IoT UE mayselect a LTE cell of a second BS, and may transmit anRRCConnectionReestablishmentRequest message to the LTE cell if theNB-IoT UE supports the LTE communication besides the NB-IoTcommunication. However, the second BS may transmit anRRCConnectionReestablishmentReject message on the LTE cell to the NB-IoTUE, since the second BS does not have a LTE context of the NB-IoT UE. Itshould be noted the first BS and second BS may be the same or different.

FIG. 5 is a flowchart of a process 50 according to an example of thepresent invention. The process 50 may be utilized in a UE (e.g., NB-IoTUE) to communicate with a BS (e.g., in the network in FIG. 1), andincludes the following steps:

Step 500: Start.

Step 502: Initiate a RRC connection reestablishment procedure for aNB-IoT communication.

Step 504: Select a LTE cell, when initiating the RRC connectionreestablishment procedure.

Step 506: Terminate the RRC connection reestablishment procedure andenter an idle mode, when selecting the LTE cell.

Step 508: End.

In one example, the UE may initiate a RRC connection reestablishmentprocedure due to detecting a RLF on a NB-IoT cell. The UE may select aLTE cell (e.g., because the UE cannot find any NB-IoT cell) in responseto the RRC connection reestablishment procedure.

In one example, the UE initiates a RRC connection establishmentprocedure by transmitting an RRCConnectionRequest message to the LTEcell, when selecting the LTE cell. That is, the UE transmits theRRCConnectionRequest message to the LTE cell instead of anRRCConnectionReestablishmentRequest message. The UE receives anRRCConnectionSetup message from the LTE cell in response to theRRCConnectionRequest message. Thus, the UE does not need to perform theRRC connection reestablishment procedure for a LTE communication. Timefor performing the RRC connection reestablishment procedure is saved.

A scenario assumed according to an example of the present invention isstated as follows. A UE is configured with a RRC connection and a DRB bya first BS via a LTE communication. The UE may detect a failure on aradio link (e.g. RLF) with the first BS, and may initiate a RRCconnection reestablishment procedure in response to the RLF. The UE mayselect a NB-IoT cell of a second BS, and may transmit anRRCConnectionReestablishmentRequest message to the NB-IoT cell if the UEsupports a NB-IoT communication. However, the second BS may transmit anRRCConnectionReestablishmentReject message on the NB-IoT cell to the UE,since the second BS does not have a NB-IoT context of the UE. It shouldbe noted the first BS and second BS may be the same or different.

FIG. 6 is a flowchart of a process 60 according to an example of thepresent invention. The process 60 may be utilized in a UE to communicatewith a BS (e.g., in the network in FIG. 1), and includes the followingsteps:

Step 600: Start.

Step 602: Initiate a RRC connection reestablishment procedure for a LTEcommunication.

Step 604: Select a NB-IoT cell, when initiating the RRC connectionreestablishment procedure.

Step 606: Terminate the RRC connection reestablishment procedure andenter an idle mode, when selecting the NB-IoT cell.

Step 608: End.

In one example, the UE may initiate a RRC connection reestablishmentprocedure due to detecting a RLF on a LTE cell. The UE may select aNB-IoT cell (e.g., because the UE cannot find any LTE cell) in responseto the RRC connection reestablishment procedure.

In one example, the UE initiates a RRC connection establishmentprocedure by transmitting an RRCConnectionRequest-NB message to theNB-IoT cell, when selecting the NB-IoT cell. That is, the UE transmitsthe RRCConnectionRequest-NB message to the NB-IoT cell instead of anRRCConnectionReestablishmentRequest-NB message. The UE receives anRRCConnectionSetup-NB message from the NB-IoT cell in response to theRRCConnectionRequest-NB message. Thus, the UE does not need to performthe RRC connection reestablishment procedure for a NB-IoT communication.Time for performing the RRC connection reestablishment procedure issaved.

A scenario assumed according to an example of the present invention isstated as follows. An NB-IoT UE in a connected mode is not able to behanded over from a cell to another cell, because a NB-IoT communicationdoes not support a connected mode mobility.

FIG. 7 is a flowchart of a process 70 according to an example of thepresent invention. The process 70 may be utilized in a UE to communicatewith a BS (e.g., in the network in FIG. 1), and includes the followingsteps:

Step 700: Start.

Step 702: Receive a handover command in a first NB-IoT cell indicating ahandover to a second NB-IoT cell.

Step 704: Synchronize to a DL of the second NB-IoT cell.

Step 706: Decode a Narrowband physical broadcast channel (NPBCH) andacquire a MasterInformationBlock-NB on the NPBCH, when synchronizing tothe DL of the second NB-IoT cell.

Step 708: Determine at least one time-frequency resource according to arandom access configuration in the handover command and according to asystem frame number (SFN) comprising a first plurality of bits and asecond plurality of bits, wherein the first plurality of bits arecomprised in the MasterInformationBlock-NB, and the second plurality ofbits are derived by the UE according to a result of decoding the NPBCH.

Step 710: Transmit a random access preamble on the at least onetime-frequency resource to the second NB-IoT cell.

Step 712: Receive a random access response comprising a UL grant, fromthe second NB-IoT cell.

Step 714: Transmit a handover complete message to the second NB-IoT cellaccording to the UL grant.

Step 716: End.

According to the process 70, the problem occurs in the above scenario issolved.

To synchronize to the DL of the second NB-IoT cell, the UE maysynchronize to at least one DL transmission or at least one DL referencesignal.

In one example, the NPBCH carries the MasterInformationBlock-NB, and istransmitted by a BS on the NB-IoT cell in a subframe #0 in every frame.the MasterInformationBlock-NB remains unchanged over a 640 ms TTI (e.g.,64 radio frames). The BS scrambles M_(bit) denoting the number of bits(i.e., the encoded MasterInformationBlock-NB) to be transmitted on theNPBCH. A scrambling sequence shall be initialized with c_(init)=N_(ID)^(Ncell) radio frames fulfilling a system frame number mode 64=0. Afterthe scrambling, the BS modulates the scrambled M_(bit) using aQuadrature Phase Shift Keying (QPSK) modulation scheme intocomplex-valued symbols. Then, the BS maps the complex-valued symbols toresource elements as below.

The complex-valued symbols y^((p))(0), . . . , y^((p))(M_(symb)−1) foreach antenna port are transmitted in a subframe 0 during 64 consecutiveradio frames starting in each radio frame fulfilling n_(f) mod 64=0, andmay be mapped in a sequence starting with y^((p))(0) to resourceelements (k,l). The mapping to resource elements (k,l) not reserved fortransmission of reference signals may be in an increasing order of firstthe index k then the index l. After mapping to a subframe, the subframemay be repeated in the subframe 0 in the 7 following radio frames,before continuing the mapping of y^((p))(⋅) to the subframe 0 in thefollowing radio frame. The first three OFDM symbols in a subframe maynot be used in the mapping process.

In one example, the UE derives the second plurality of bits according tothe result of decoding the NPBCH as follows. The UE identifiesboundaries of a 80 ms period (e.g., 8 radio frames) by decoding at leastone of a narrowband primary synchronization signal (NPSS) and anarrowband secondary synchronization signal (NSSS), and identifies alocation of the 80 ms period in the 640 ms TTI by descrambling the NPBCHaccording to (e.g., using) a scrambling sequence. That is, the UE knowsthe boundaries of the 640 ms TTI according to the location. The UEderives the second plurality of bits (e.g., the least significant 6bits) from the boundaries of the 640 ms TTI. When the UE acquires theMasterInformationBlock-NB, the UE gets the first plurality of bits(e.g., the 4 most significant bits), and constructs the system fromnumber as the 10 bits (i.e., 4 bits+6 bits).

When the UE receives a handover command in a first LTE cell, indicatinga handover to a second LTE cell, the UE may not need to acquire a SFN ofthe second LTE cell, when the UE determines the time-frequency resource(s) for the transmission of the random access preamble on the second LTEcell. The UE determines the time and frequency resource(s) (e.g., only)according to the random access configuration in the handover command,when the UE synchronizes to the second LTE cell (e.g., framesynchronization). The UE may acquire the SFN, after transmitting therandom access preamble, after receiving the random access response orafter transmitting the handover complete message.

Those skilled in the art should readily make combinations, modificationsand/or alterations on the abovementioned description and examples. Theabovementioned description, steps and/or processes including suggestedsteps can be realized by means that could be hardware, software,firmware (known as a combination of a hardware device and computerinstructions and data that reside as read-only software on the hardwaredevice), an electronic system, or combination thereof. An example of themeans may be the communication device 20. Any of the above processes andexamples above may be compiled into the program code 214.

To sum up, the present invention provides a device and a method forhandling a NB-IoT communication. Reception of system information,selection of a NB-IoT cell or a LTE cell and a handover procedure can beprocessed by a UE (or a NB-IoT UE) correctly.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A communication device for handling a narrowbandinternet of things (NB-IoT) communication, comprising: a storage device,for storing instructions of: receiving a SystemInformationBlockType2-NBmessage broadcasted by a base station (BS) on an NB-IoT cell; receivingan RRCConnectionReconfiguration-NB message indicating a fullconfiguration, from the BS on the NB-IoT cell; using a plurality ofvalues for timers T301, T310, T311, constant N310 for counting thenumber of consecutive “out-of-sync” indications for the NB-IoT cell, andconstant N311 for counting the number of consecutive “in-sync”indications for the NB-IoT cell in response to theRRCConnectionReconfiguration-NB message, wherein the values arecomprised in the SystemInformationBlockType2-NB; starting the timerT310, when detecting N310 consecutive “out-of-sync” indications for theNB-IoT cell; starting the timer T311, when the timer T310 expires;starting the timer T301, when the UE selects the NB-IoT cell while thetimer T311 is running; and stopping the timer T310, when detecting N311consecutive “in-sync” indications for the NB-IoT cell; and a processingcircuit, coupled to the storage device, configured to execute theinstructions stored in the storage device.
 2. A method for handling anarrowband internet of things (NB-IoT) communication, comprising: astorage device, for storing instructions of: receiving aSystemInformationBlockType2-NB message broadcasted by a base station(BS) on an NB-IoT cell; receiving an RRCConnectionReconfiguration-NBmessage indicating a full configuration, from the BS on the NB-IoT cell;using a plurality of values for timers T301, T310, T311, constant N310for counting the number of consecutive “out-of-sync” indications for theNB-IoT cell, and constant N311 for counting the number of consecutive“in-sync” indications for the NB-IoT cell in response to theRRCConnectionReconfiguration-NB message, wherein the values arecomprised in the SystemInformationBlockType2-NB; starting the timerT310, when detecting N310 consecutive “out-of-sync” indications for theNB-IoT cell; starting the timer T311, when the timer T310 expires;starting the timer T301, when the UE selects the NB-IoT cell while thetimer T311 is running; and stopping the timer T310, when detecting N311consecutive “in-sync” indications for the NB-IoT cell; and a processingcircuit, coupled to the storage device, configured to execute theinstructions stored in the storage device.